In the art of earth work, various means have been used to contain, divert, intercept and control subsurface flows of water. The prior art methods utilize soil cements, mortars, grouting, concrete and the like to construct subsurface walls. These methods and materials have the drawbacks of difficult excavation and expensive materials being used in a dig and pour construction of the wall below grade. Also, the substantial rigidity of the finished wall can lead to problems with cracks and leaks caused by settling, subsidence, as well as unequal hydraulic pressures upon opposite sides, or even below, these walls. Also, non-structural members and sheeting have been used for subsurface barrier walls, for example, by rolling the material into a pre-dug trench using the methods and apparatus in U.S. Pat. No. 5,320,454. Still, excavation before installation of the wall is necessary. Also, the non-structural barriers cannot withstand vertical or full horizontal loading. All the drawbacks of these prior art methods and apparatus are accompanied with the difficulties of repair or maintenance to the wall, because a second excavation is required to remove, replace or repair any portion of the wall. The prior art barrier walls typically require welding of the panel or sheet to a connector means. Thus, a need exists for a method and means for forming a subterranean wall that seals off aqueous flows and which can be installed, removed or replaced without expensive excavation.
The prior art discloses locking edges that join panels for use as bulkheads, however, in that and similar applications, seepage of liquids through the lock is acceptable, as a means of equalizing the liquid pressure on either side of the bulkhead. These prior art edges joined the members, but within the joint there was limited surface contact between the edges, and so seepage could occur. The usefulness of increasing the surface contact area between the interlocking edges to form a more effective moisture barrier was recited in U.S. Pat. No. 5,320,454, which used a plurality of interlocking slots and channels. A need exists for a simpler and more efficient means of increasing surface contact and of improving the seal in the interlock between the members that form the barrier wall. To fulfill these needs and to overcome the limitations of the prior art methods and apparatus, the invention described and claimed here provides improved interlocking edges, and also, a means of sealing the interlock between the sheet piles, so that persons skilled in the art can form a subterranean wall that is substantially impervious to liquid flows.